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4adcf7fb67
ipath_user_sdma_queue_pkts() gets called with mmap_sem held for writing. Except for get_user_pages() deep down in ipath_user_sdma_pin_pages() we don't seem to need mmap_sem at all. Even more interestingly the function ipath_user_sdma_queue_pkts() (and also ipath_user_sdma_coalesce() called somewhat later) call copy_from_user() which can hit a page fault and we deadlock on trying to get mmap_sem when handling that fault. So just make ipath_user_sdma_pin_pages() use get_user_pages_fast() and leave mmap_sem locking for mm. This deadlock has actually been observed in the wild when the node is under memory pressure. Cc: <stable@vger.kernel.org> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com> [ Merged in fix for call to get_user_pages_fast from Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>. - Roland ] Signed-off-by: Roland Dreier <roland@purestorage.com> |
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